<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<div id="app">
    <button v-on:click="sayhey">点我</button>
</div>
<script src="https://cdn.jsdelivr.net/npm/vue@2.5.16/dist/vue.js"></script>
<script>
    var vm=new Vue({
        el:"#app",
        data:{
            message: "黄嘉文"
        },
        methods:{//方法必须定义在vue的methods中
            sayhey: function () {
                alert(this.message)
            }
        }
    });
</script>
</body>
</html>